1. Field of the Invention
The present invention relates to mobile telephones or a wireless local loop (hereinafter denoted as WLL) subscriber terminal, and in particular, to a mobile telephone with an accounting function which enables a user to check a call charge through a display unit and a method for controlling the same.
2. Description of the Related Art
When using a mobile telephone as well as a WLL subscriber terminal, occasionally there is a need for checking the call charge and charging the fare accordingly for the telephone call. For example, in order to offer convenience to the fare (or passenger), a public mobile telephone is installed in a taxi. The taxi driver measures the call duration to charge the fare for the call by using a separate billing apparatus installed in the taxi. The billing apparatus is connected to the mobile telephone via an RS-232C interface, and calculates the call charge based on the call information received from the mobile telephone.
FIGS. 1A through 1G show a display unit of a known mobile telephone, on which various call information is displayed. Specifically, FIG. 1A shows a state where the mobile telephone has been engaged (i.e., in a busy state) for a call duration of 1 minute and 20 seconds; FIG. 1B shows a state where the mobile telephone is dialing the telephone number; FIG. 1C shows a state where the mobile telephone is just connected to a mobile telephone switching office (MTSO); FIG. 1D shows a call time for the last outgoing call; FIG. 1E shows the air time display (i.e., a call duration accumulated up to the present); FIG. 1F shows the called number for the last call, and FIG. 1G shows the last call information including the date and time when the last call was made, respectively.
As illustrated above, the known mobile telephone merely displays the call time and call duration for the previous calls. Thus, when the billing apparatus is not installed in the public mobile telephone, the user (i.e., the driver or fare) is required to manually calculate the call charge based on the call time and call duration displayed on the display unit. This manual calculation is inconvenient and can result in miscalculation. In practice, the call duration begins to be counted, once the mobile telephone is connected to the mobile telephone switching office, regardless of whether the other party answers the outgoing call, as shown in FIG. 1C. Therefore, the displayed call duration may be different from the actual call duration, which leads to additional miscalculation.